1. Technical Field
This device relates to the testing of telephone lines and line repeaters used in the telecommunication industry which employ the generation of a test signal loop.
In the telecommunication industry telephone central offices (C.O) are connected by cables forming networks of "twisted wire pairs". The local telephone service provider is usually a local exchange carrier (LECS). There are also inter-exchange carriers (IXCS) that connect to the (LEC'S) to form the national network.
There are a number of different "access transport technologies" that are used to connect to a network such as ISDN, T-1, T-3, ATM, and SONET.
To access a network you need an access point and a transport facility or physical connection referred to generally as pipes. The simplest access pipe is an analog phone line that is then converted to digital by pulse code modulation and transported over the network at 64,000 BPS (Bits Per Second) defining one channel. A high-cap or T-1 line combines 24 digitized voice channels into one pipe using only two twisted wire pairs. The twisted wire pairs carry parallel transmissions. In the T-1 transmission format, the 24 channels each add 64,000 BPS combined to define the T-1 rate of 1.544 MBPS (million bits per second). Typically, signal repeaters are installed on the twisted wire pair between the central offices to regenerate the signals transmitted due to signal transmission distance limitation which inherently limits the overall distance that an effective signal can be sent without substantial degradation. Equipment faults or other line problems can occur in the transmission between the central offices and the end user. To pinpoint the faults along a T-1 line can be a difficult and time consuming task which requires line inspection and electronic testing of the line segments to isolate the problem.
To test a T-1 transmission span, it normally must be powered and accordingly requires "test equipment" that enables the line typically referred to as a "power lid" which works only on standard repeater spans.
The problem of testing is compounded in new insulations where the testing technician needs to wait for the central office (CO) to be wired before testing the line to the customer.
It is accordingly an object of this invention to overcome such problems by replacing the required "power lid" with a portable testing device capable of generating a simple go/no-go test signal loop at any location along the T-1 line without requiring central office to be wired, as noted above.
2. Description of Prior Art
Prior art devices of this type have relied on a variety of different configurations to test and configure T-1 telecommunication lines, see for example U.S. Pat. Nos. 3,965,309, 5,224,149, 5,060,226, 5,317,278, and 5,422,929.
U.S. Pat. No. 3,965,309 is directed to a test system that converts typical trio type pulse sets to quadruple sets.
U.S. Pat. No. 5,060,226 is a test system for digital telecommunication networks by a master test unit in combination with at least one remotely addressable field loop back unit.
U.S. Pat. No. 5,317,278 is a switched A-clip fault locator filter that combines multiple filters requires in a single unit.
U.S. Pat. No. 5,224,149 is a testing system for digital transmission lines with a metallic loop back and direct current by-pass for use with regenerative repeaters.
U.S. Pat. No. 5,422,929 is directed to a telephone line repeater and method of testing same wherein an inter-alia and input signal is transmitted on a telephone network that indicates an address field with at least one sub-field.